This project is aimed toward the development of a theory of hydrogen bonding, to be established by analyzing the results of ab initio self-consistent field molecular orbital calculations on various series of hydrogen bonded dimers, and on larger hydrogen bonded polymers. Some specific goals of this work are: (1) to determine the equilibrium structures and energies of various series of hydrogen bonded dimers, and to characterize the chemical moieties which act either as proton donors or proton acceptors in these dimers; (2) to evaluate the influence of primary and secondary factors on dimer structures and stabilities, and to examine substituent effects on the hydrogen bond; (3) to compute and analyze various properties of hydrogen bonded dimers, making correlations with experimental data where possible, and noting the implications for hydrogen bonding in more complex biological systems; (4) to further investigate hydrogen bonding through pi electron systems in aromatic compounds, and to relate the results of this study to the solvation of these bases; (5) to study the protonation of these same bases, and to analyze the relationship between protonation and hydrogen bond formation; and (6) to further test and refine the General Hybridization Model, to note its application to hydrogen bonding in biological systems, and to incorporate the results of this research on small systems into a model for describing hydrogen bonding in more complex biological systems. BIBLIOGRAPHIC REFERENCES: J. E. Del Bene, "Molecular Orbital Theory of the Hydrogen Bond. X. Monosubstituted Carbonyls as Proton Acceptors" J. Chem. Phys. 62, 1314 (1975). J. E. Del Bene, "Molecular Orbital Theory of the Hydrogen Bond. XI. The Effect of Hydrogen Bonding on the Transition in Dimers HOH...OCHR" J. Chem. Phys. 62, 666 (1975).